Volume 15 Issue 1

Wood-plastic composites (WPCs) have become one of the most remarkable materials for construction in recent years. Along with high resistance against biological threats, the high mechanical properties are also desired from WPCs as well. In this study, polypropylene (PP) and polyethylene (HDPE) based flat-pressed WPC specimens were reinforced with woven fiber fabric to gain higher mechanical properties. Woven fabrics were located 20% (w/w) below for both surfaces. Carbon fiber and glass fiber woven fabrics, known to have high mechanical properties, were preferred to improve screw withdrawal resistance (SWR) of WPC. Specimens were produced with different wood flour contents (40, 50, and 60%). Results indicated that the increase of SWR reached up to 83%. The highest increase was obtained from carbon fiber for PP, while it was glass fiber for HDPE fabric. The coupling agents had a positive effect on SWR. This study also showed that PE based WPCs had higher SWR compared to PP based ones. Moreover, as wood flour content increased, SWR decreased. The surface roughness of WPCs was also investigated. Contrary to SWR, the wood flour content positively affected the surface roughness; i.e., as wood content increased, surface roughness of WPCs increased. The structure of specimens were also examined using SEM.

A method was developed to reduce isothiazolinone (MCI/MI) leaching from treated bamboo, thereby extending the service life of bamboo. In this study, the self-healing coatings were prepared by incorporating 10 to 12 wt% microcapsules of urea-formaldehyde resin (UF)/tung oil into conventional polyurethane varnish and acrylate varnish. In the leaching test, the self-healing coatings outperformed the control coatings. Compared with the control coatings, the average leaching rates coated by the polyurethane and acrylate self-healing coatings were reduced by 6.22% and 6.29%, respectively. In impact damage and adhesion strength tests, the ability of the self-healing coatings to withstand damage was close to the control coatings. The results indicated that self-healing coating is a feasible method to reduce the leaching of MCI/MI from treated bamboo.

Kenaf (KNF) was treated at room temperature with the amino acid lysine. The surface treatment of KNF using lysine was studied for the first time on prepared composites with linear low-density polyethylene, poly(vinyl alcohol), and kenaf. The LLDPE/PVOH/KNF composites with different loadings of lysine-treated and untreated KNF were studied at levels of 10, 20, and 40 parts per hundred resin (phr). The melt mixing of all the composites were prepared by using an internal mixer for 10 min at a temperature and rotor speed of 150 °C and 50 rpm, respectively. The results showed that tensile strength and tensile modulus were improved for the lysine-treated KNF composites compared to the untreated KNF composites. Fourier transform infrared (FTIR) spectroscopy revealed the presence of protonated amino (NH3+) and carboxylate (COO-) groups in the LLDPE/PVOH/KNF composites after the lysine treatment. Scanning electron microscopy analysis showed good adhesion between the lysine treated KNF and the LLDPE/PVOH matrices. Thermogravimetric analysis (TGA) showed that the lysine treated KNF composites possessed a higher thermal stability than the untreated KNF composites.

In this study, a wood-based X-type lattice sandwich structure was fabricated by an insertion glue method using medium density fiberboard (MDF) and plywood as panels. Birch was used for the core. The mechanical properties and failure modes of the wood-based X-type lattice sandwich structure were investigated by an out-of-plane compressive test, a short beam shear test, and their matching analytical models. The out-of-plane compressive test and the compression analytical model showed that the failure mode of the plywood and birch combination was mainly shear failure in the core. The cores were broken or had sliding surfaces, while the failure mode of the MDF and birch combination was mainly shear failure of the core at both ends. Although the compression properties of the MDF and birch combination were better, the specific strength and modulus of the plywood and birch combination was larger, which align with the characteristics of lightweight and strong strength. The failure mode of the plywood and birch combination was delamination at both ends of the panel or core breakage, which indicated that this combination had better short beam shear properties. The theoretical models of the compressive /short beam shear properties were in good agreement with experimental results obtained for the plywood and birch combination.

Enzymolysis is a key bioconversion process of lignocellulosic biomass. The optimization of enzymolysis is important for its efficiency and accuracy. There is potential to solve the problem of low reducing sugar in the conversion of lignocellulose to bioethanol. In this study, mixed cellulases (cellulase and β-glucosidase) were used in the enzymolysis of acid-exploded poplar wood residues. The mixed enzymolysis process was optimized by response surface area test, and its kinetics model was established based on the Michaelis-Menten equation. The optimal parameters of the mixed enzymolysis were: initial, pH 5.2; temperature, 46 °C; and cellulase to β-glucosidase ratio, 1.62. These parameters resulted in enzymatic saccharification efficiency 1.3 times as high as that of the control (conducted with un-optimized parameters). The modeling revealed that there was a strong correlation (R2 = 0.97) between substrate concentration and reaction rate. Multiple simultaneous saccharification and cofermentation (MSSCF) developed in the laboratory was also employed to verify the optimal parameters. The mixed enzymolysis process carried out with the optimal parameters achieved an ethanol concentration of 30.09 ± 0.49 g/L, which was 1.64 times higher than that conducted with un-optimized parameters. The fermentation time was also reduced by 24 h. Overall, the optimization of mixed enzymolysis process could enhance the efficiency of lignocellulosic directional conversion to bioethanol.

The wood fiber industry has a complex and sensitive supply chain. Consumers and suppliers across the wood fiber supply industry share a highly dynamic relationship, but they lack a structured technique to evaluate and improve the flow of information and materials. The goal of this study was to develop a mathematical model based on supplier selection and assessment criteria using structured, multi-criteria decision-making methods. The first method was the analytic hierarchy process (AHP) and the second method was the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS). These methods were chosen based on their acceptance and use in previous research. The hybrid model was implemented as a software tool based on Microsoft Excel and Visual Basic. The tool improved the way in which wood product firms selected their suppliers and guaranteed that the best available alternatives were selected, thus increasing the chance of a successful supplier-consumer relationship and increasing the value that the company receives from its supplier base. Seven interviews were conducted in the wood fiber industry to validate the tool. The tool was found to be applicable and a valuable approach, as reported by most participants.

A cost-effective, eco-friendly, and health-promoting packaging system that prevents the passage of greases and oils would fulfill an urgent need. This review discusses what is known about the highly divergent technological paths that have been studied to achieve these objectives. Before the emergence of plastic films, the paper industry addressed these objectives in two ways, by parchmentizing and by high levels of refining of the fibers. Parchmentizing means passing the paper through a bath of concentrated sulfuric acid, followed by rinsing out the acid and drying the sheet. Though both parchmentized paper and highly refined greaseproof paper products are still made, they have been substantially displaced by oil-repellent fluorocarbon treatments of paper. The fluorocarbon treatments have allowed papermakers to achieve greaseproof properties with ordinary paper machine equipment at ordinary refining levels and without a need to immerse the paper in strong acid. Now, however, due to environmental concerns and regulations, the paper industry needs more options. Some promising directions in published research include advances in chemistry, superoleophobic surfaces, nanocellulose films, and systems to protect nanocellulose films from the effects of moisture.

α-Amylases (E.C 3.2.1.1) hydrolyse starch into smaller moieties such as maltose and glucose by breaking α-1,4-glycosidic linkages. The application of α-amylases in various industries has made the large-scale productions of these enzymes crucial. Thermostable α-amylase that catalyses starch degradation at the temperatures higher than 50 °C is favourable in harsh industrial applications. Due to ease in genetic manipulation and bulk production, this enzyme is most preferably produced by microorganisms. Bacillus sp. and Escherichia coli are commonly used microbial expression hosts for α-amylases (30 to 205 kDa in molecular weight). These amylases can be purified using ultrafiltration, salt precipitation, dialysis, and column chromatography. Recently, affinity column chromatography has shown the most promising result where the recovery rate was 38 to 60% and purification up to 13.2-fold. Microbial thermostable α-amylases have the optimum temperature and pH ranging from 50 °C to 100 °C and 5.0 to 10.5, respectively. These enzymes have high specificity towards potato starch, wheat starch, amylose, and amylopectin. EDTA (1 mM) gave the highest inhibitory effect (79%), but Ca2+ (5 mM) was the most effective co-factor with 155%. This review provides insight regarding thermostable α-amylases obtained from microbial sources for industrial applications.

This review article considers published evidence regarding effects of particle size on mechanical properties of plastic matrix materials filled with cellulose-based reinforcements. Cellulosic or wood-based reinforcements in plastic matrices can contribute to higher modulus, lower density, and less tendency to sag in comparison with the matrix phase by itself, while still allowing the resulting material to be cut or milled. Although cellulosic materials are generally too hydrophilic to adhere well to common thermoplastic materials such as polyethylene, such deficiencies can be overcome by use of compatibilizers, e.g. polyethylene-maleic anhydride. Recently many researchers have evaluated nanocellulose in plastic composites. The higher surface areas of nanocellulose generally imply a higher cost of compatibilizer to achieve good interfacial adhesion. This review first examines results of a large number of studies all involving high-density polyethylene as the matrix. Then, to get a more detailed mechanistic view, studies are considered that compare different particle sizes of cellulose-based reinforcements within the same conditions of preparation of composites prepared with various matrix polymers. To summarize the findings, there does not appear to be any consistent and dependable advantage of using nano-sized cellulosic reinforcements when trying to achieve higher values of composite strength or modulus.

The aim of this review is to examine the problems encountered with logs kept in depots and the measures recommended to correct them. Biotic, abiotic, and other factors can affect the quality and quantitative properties of stored logs. Biotic factors include fungi (decay/rot fungi, stain fungi, and mold), insects (wood, bark, and ambrosia beetles), and bacteria. The climatic conditions of ultraviolet (UV) light, wind, and temperature at the storage site can be considered as abiotic factors. In addition, storage problems may be caused by business management, inadequate training and qualifications of depot personnel, and the type of depot floor/ground. Measures to counteract these factors were examined in detail, as a result of field observations and literature studies. The solutions presented included: shortening the storage period and expanding winter production rather than maintaining year-round storage, bringing production planning in line with the needs of the sector and providing sufficient training to workers and technical personnel, as well as increasing the sale of standing trees, separating earlier- and later-felled products in depot areas, installing pheromone traps, and ensuring proper drainage and maintenance of depot grounds. Additional measures to be taken in factory warehouses included water sprinkling and holding logs in water (ponding).